Rectifier



May 10 949. a. LEVHN 2,459,393

RECTIFIER Filed Feb. 8, 1945 INVENTOR. IRVIN LEVIN BY WJMW m ATTORNEY Patented May 10, 1949 UNITED STATES PATENT OFFICE RECTIFIER Irvin Levin, Asbury Park, N. J.

Application February 8, 1945, Serial No. 576,864

3 Claims. (01. 175-366) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 O. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

My invention relates to alternating current rectifiers and more particularly to the dry disc type rectifier.

The dry disc type rectifier field at present comprises three different types of rec-tifiers, namely, the copper sulphide, the copper oxide and the selenium.

An object of my invention is to provide a method of construction of a dry disc type rectifier which can be easily assembled in the laboratory.

Another object of my invention is to provide a method of construction of the discs which are more easily formed chemically. Another object of my invention is to provide a method of construction of an iron oxide-magnesium dry rectifier, in which the purity of the iron does not have to be important.

My invention was conceived by the need of a dry disc type rectifier which could easily be made in the laboratory. My dry disc type rectifier is much easier to form chemically in the laboratory than the copper oxide, copper sulphide and the selenium types. Only a flame or other source of heat is required for the formation of the iron oxide barrier layer, whose chemical name is ferroso-ferric oxide, whereas in the copper oxide and copper sulphide types critical temperatures and manipulations are required. The purity of the iron does not appear to be as important a problem as with the copper used in the copper containing rectifiers. In fact, the iron oxidemagnesium rectifiers can utilize mild steel or other ordinary steels commonly met with. The iron and magnesium discs can be at least as thin as 5 mils. The iron disc is heated at red heat for about three minutes on a sheet of asbestos mounted on a tripod by .using a Bunsen flame or other source of heat. This allows a layer of the magnetic ferroso-ferric oxide to form'over the surface of the iron disc. The iron disc is allowed to cool to the black color. The magnesium disc, which has a clean surface, is placed on the hot iron disc which contains the ferroso-ferric layer, pressed together immediately and the combination allowed to cool. The combination is assembled as a rectifier unit and tested for its D. C. to A. C. ratio. 0.636 is the limiting value of this ratio for perfect half-wave rectification. However, an oscilloscope check may be performed or even substituted for the above ratio test.

If the combination is found to rectify poorly, it is removed from the assembly and reheated carefully with a. fiame or other source of heat with the magnesium disc resting on top of the unit. Great caution is needed to prevent the melting or burning of the magnesium.

The rectifying layer can carry a current den sity (and rectify), as read on a D. C. meter, of 250 milliamperes per square inch, which is the maximum optimum amount. The D. C. to A. C. ratio changes very little with temperature, which rises to approximately 40 C. at the above current density of 250 milliamperes per square inch. All frequencies used were 60 cycles per second, but it does not necessarily mean that the frequency is limited to 60 cycles. Raising the voltage over the optimum maximum value does not impair the rectifying action when brought back to normal.

My invention will be more fully understood from the following detailed description taken in connection with the accompanying drawing wherein I have shown a preferred embodiment thereof.

In the drawings,

Figure 1 is an exploded view of a rectifier embodying my present invention; and

Figure 2 is an elevational view of said rectifier when in its assembled operative condition.

Fig. 1 shows an exploded view of my invention comprising: bolt HI, steel washers ll, radiator electrodes [12, iron disc with an oxide layer l3, magnesium disc M, insulating gasket 15 and nut it. The holes in steel Washers ii and insulating gasket l5 are of small diameter so as to be closely fitted around bolt Hi. When the rectifier is assembled the bolt l 0 is co-axially centered in the larger diameter holes of the radiator electrodes I2, iron disc with an oxide layer l3 and magnesium disc l4, so as to allow the current'to enter only at wire terminal l'i, pass through the iron disc with an oxide layer 83 in contact with the magnesium disc I4 and the circuit is completed through the rectifier at terminal l8 without making electrical contact between bolt III, radiator electrode l2 adjacent to insulating gasket l5, and said discs 53 and iii.

Fig. 2 shows a complete rectifier assembly comprising: an iron disc with an oxide layer 13 in surface contact with a magnesium disc 14, radiator electrodes 12, suitable insulating gasket l5 and metal washers II. This assembly as shown is clamped securely by bolt in and nut I6, said bolt l0 and nut l6 insulated from the rectifying Y circuit as shown and described in Fig. 1. Elecradiator electrodes It for connecting the rectifier in an electric circuit for rectifying purposes.

Having thus described my invention I desire to secure by Letters Patent and claim:

1. The method of making an iron oxide-magnesium rectifier unit which comprises providing iron and magnesium discs having a thickness of the order of 5 mils, heating said iron disc at red heat for a period of time suflicient to form a layer of magnetic ferroso-ferric oxide over a surface of said iron disc, cooling said iron disc to the black color, immediately applying a clean surface of said magnesium disc in contact with said layer of the hot iron disc, pressing said discs together and permitting the same to cool to a lower temperature and assembling the discs in the rectifier unit.

2. The method of making an iron oxide-magnesium rectifier unit which comprises providing iron and magnesium discs having a thickness of the order of 5 mils, heating said iron disc at red heat for a period of time suificient to form a layer of magnetic ferroso-ferric oxide over a surface of said iron disc, cooling said iron disc to the black color, immediately applying a clean surface of said magnesium disc in contact with said layer of the hot iron disc, pressing said discs together and permitting the same to cool to a lower temperature and assembling the discs in the rectifier unit, testing said rectifier unit with respect to a limiting value of 0.636 as determined for perfect half,-wave rectification and reheating the disc assembly through the iron disc with the magnesium disc furthest from the heat source until the limiting value is attained.

3. The method of making an iron oxide-magnesium rectifier unit which includes the steps of heating a fiat iron member to red heat to form a layer of iron oxide on one surface thereof, cooling said member to the black color, immediately placing a fiat magnesium member into contact with said oxide layer of the hot iron member and applying pressure so as to effect intimate contact between the magnesium and the oxide, permitting the parts aforesaid to cool while subjected to such pressure, and assembling the same in a rectifier unit.

IRVIN LEVIN.

vREFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain Apr. 12, 1938 Number Number 

